Complex Gyrator Circuits of Planar Circulators Using Higher Order Modes in a Disk Resonator

Tire use of resonators or waveguides utilizing higher order modes is often an attractive solution to the design of millimeter microwave networks. This paper investigates the complex gyrator circuit of a planar junction circulator employing higher order solntions in a disk resonator. The first such solution displays many of the features of weakly magnetized junctions using the dominant mode in a disk resonator, but its loaded Q-factor is incompatible with the realization of quarter-wave coupled devices. Although the second one exhibits more useful equivalent circuits, it requires a relatively large magnetization, which is not altogether practical at millimeter frequencies. A circulator configuration that has a frequency response akin to that of a quarter-wave coupled one is one where the in-phase eigennetwork is degenerate with those of the demagnetized counter-rotating eigennetworks. The degeneracy between the in-phase limit, TM _{2, 0, -2} and the second-order counter-rotating limit, TM _{1, 1, -2} modes, in an oversized irregular hexagonal resonator, is used in this paper to construct such a device.